1. Field of the Invention
The present invention relates to steering systems and, in particular, to a steering system for docking a marine vessel.
2. Description of the Related Art
In conventional steering systems for docking a marine vessel an operator uses a joystick to maneuver the marine vessel. The joystick allows the operator to maneuver the marine vessel in lateral direction, i.e. in a direction which is substantially perpendicular to a longitudinal axis of the marine vessel. This lateral directional movement is achieved by independently steering the propulsion units of the marine vessel to effect vector thrusting. For example, in a marine vessel provided with two propulsion units, shifting one of the propulsion units into reverse and simultaneously shifting the other propulsion unit into forward while selectively adjusting the steering angles of the propulsion units can cause the marine vessel to move in a lateral direction. The joystick controls both steering functions and shift and control functions during docking. The conventional steering systems are also typically provided with a helm for steering the marine vessel on open water and a control levers for controlling shift and throttle functions on open water.
An example of a conventional steering system for docking a marine vessel disclosed in U.S. Pat. No. 6,994,046 which issued on Dec. 23, 2008 to Kaji et al. The steering system disclosed by Kaji et al. includes a helm, a control lever, a joystick, and a pair of propulsion units. The helm and control lever are used to maneuver the vessel in an ordinary running mode in which the steering angles of the propulsion units are substantially equal to each other. The joystick is used to maneuver the vessel in a lateral movement mode in which the steering angles of the propulsion units are independently adjusted to achieve lateral movement of the marine vessel. The steering system is operative in the ordinary running mode when input from the helm or control lever is detected and is operative in the lateral movement mode when input from the joystick is detected. It accordingly may not be possible to use the joystick in the ordinary running mode.